#include <stdio.h>

int main() 
{
    int r1 = 0;
    int r2 = 0;
    scanf("%d %d",&r1,&r2);

    float r3 = 1.0 / r1;
    float r4 = 1.0 / r2;
    float R = 1.0 / (r3 + r4);

    printf ("%.1f",R);

    return 0;
}